frenzy/lib/frenzy_web/plug/authenticate.ex

defmodule FrenzyWeb.Plug.Authenticate do
  import Plug.Conn
  alias Frenzy.{Repo, User}
  alias FrenzyWeb.Router.Helpers, as: Routes
  alias FrenzyWeb.Endpoint

  def init(opts), do: opts

  def call(conn, _opts) do
    user_token = get_session(conn, :user_token)

    case Phoenix.Token.verify(Endpoint, "user token", user_token, max_age: 24 * 60 * 60) do
      {:error, _reason} ->
        conn
        |> Phoenix.Controller.redirect(
          to: Routes.login_path(Endpoint, :login, continue: Phoenix.Controller.current_path(conn))
        )
        |> halt()

      {:ok, user_id} ->
        case Repo.get(User, user_id) do
          nil ->
            conn
            |> Phoenix.Controller.redirect(to: Routes.login_path(Endpoint, :login))
            |> halt()

          user ->
            user = Repo.preload(user, [:groups, :feeds])
            assign(conn, :user, user)
        end
    end
  end
end